Comparative study of the antioxidant and antibacterial activities of Rumex abyssinicus with commercially available Zingiber officinale and Curcuma longa in Bahir Dar city, Ethiopia

Abstract Background Rumex abyssinicus (RA) is one of indigenous plants to Ethiopia having traditional values during butter refinement in rural areas. This paper presents a comparative study of the antioxidant and antibacterial activities of RA sample extract to that of Zingiber officinale (ZO) and Curcuma longa (CL). Methods Phytochemical screening tests were, first, done using different confirmatory tests prior to quantitative determinations. Quantitative determinations were then conducted—the total phenolic content by the Prussian blue method, total flavonoid content by the aluminum colorimetric assay, and antioxidant activity by the reducing power assay and the cyclic voltammetry technique. Results All of the samples showed positive tests, with different intensities, for the presence of phenolics, flavonoids, glycosides and tannins, but not for alkaloids. The total phenolic content, the total flavonoid content and the antioxidant activities of RA (in mg/100 g dry weight) were found to be 319.208 ± 15.997, 113.252 ± 1.702 and 45.632 ± 2.026, respectively. On the other hand, both oxidation and reduction peaks were observed in the cyclic voltammetry analysis of the herbs, showing a quasi-reversible redox process of their phenolic compounds. The determination of the inhibition zones (in mm) of ethanol extract of RA was found to be 20.33 ± 0.58, 21.67 ± 0.58, 19.17 ± 0.29, 18.17 ± 0.29, and 21.67 ± 0.58 against Staphylococcus aureus, MRSA, Streptococcus pneumonia, Escherichia coli, and Shigella flexneri bacteria strains, respectively. Conclusion The substantial antioxidant and antibacterial activities of RA compared to ZO and CL indicate that the traditional use of the herb to refine butter and keep it safe longer without rancidity formation and other traditional medicinal practices can be attributed to both its antioxidant and antibacterial activities.